The exemplary embodiment relates to registration of images in printing systems. It finds particular application in connection with a registration system for a multicolor printing system which compensates for fluctuations in the position of an image receiving surface between marking stations.
Ink jet printing involves ejecting ink droplets from orifices in a print head onto a receiving surface to form an image. The image is made up of a grid-like pattern of potential drop locations, commonly referred to as pixels. The resolution of the image is expressed by the number of ink drops or dots per inch (dpi), with common resolutions ranging between 200 dpi and 1200 dpi.
Ink-jet printing systems commonly utilize either a direct printing or offset printing architecture. In a typical direct printing system, ink is ejected from jets in the print head directly onto the final receiving media web, or web for short. In an offset printing system, the image is formed on an intermediate transfer surface and subsequently transferred to the final receiving web. The intermediate transfer surface may take the form of a liquid layer that is applied to a support surface, such as a drum. The printhead jets the ink onto the intermediate transfer surface to form an ink image thereon. Once the ink image has been fully deposited, the final receiving web is then brought into contact with the intermediate transfer surface and the ink image is transferred to the final receiving web.
The architecture of continuous feed (CF) direct marking (DM) printers includes the use of multiple printheads (or marking stations) distributed into several color printhead modules along the printing path. Some printers have as many as six color modules with four print units per color module incorporating fourteen printheads. Direct marking from an array of independent printheads on a continuous feed printer requires tight registration between the heads to prevent image artifacts. One of the phenomena observed in CF printing systems is the stretching of the web. This distortion of the web in the process direction causes image miss-registration and printed image length variation, the amounts of which are determined by web tension and Young's Modulus. The registration can be achieved, and the length variation can be eliminated by employing advanced techniques such as Double Reflex Printing (DRP), if Young's Modulus of the media is known. Details on double reflex printing can be found, for example, in U.S. Pat. Pub. No. 2008/0124158 A1, the disclosure of which is hereby incorporated by reference in its entirety. Measurement of the Young's Modulus is typically done by off-line experiments, as these measures are limited to small samples of the media. However, the Modulus can vary within a web roll, from the outer to the inner core of the roll, or from batch to batch, or by media types, which affects the printed image length, thereby having a negative impact with respect to the color-to-color registration.
The exemplary embodiments contemplate a new and improved method and system that resolves the above-referenced difficulties and others.